Cambelt + Water Pump Replacement - Official guidance

[clarinetbcn]

The timing must have been out .. it was stalling easily if not in exactly in the correct gear .. if I slowed down too much at a roundabout for example .. like there was a missing gear ... after the cam belt was done I could go slow in third gear easily .. I had never driven a t6 before so didn’t realise how bad mine was until this job was done ... and of course the water pump had also started leaking ..

I think there may be a basic misunderstanding about ignition timing, which on diesel motors is controlled by the compression cycle and glow plugs and is not adjustable as there are no spark plugs, injection timing of the fuel, which is electronically controlled, and cam belt timing, which controls the physical relationship between the movement of the valve train and the pistons. If that is not correct there could be catastrophic damage to the engine, even if the belt itself is in perfect condition. Sounds like there was something else going on. If I were told by a mechanic that stalling on a roundabout could be remedied by changing the cam belt, I would find a different mechanic.

 

[osman]

I think there may be a basic misunderstanding about ignition timing, which on diesel motors is controlled by the compression cycle and glow plugs and is not adjustable as there are no spark plugs, injection timing of the fuel, which is electronically controlled, and cam belt timing, which controls the physical relationship between the movement of the valve train and the pistons. If that is not correct there could be catastrophic damage to the engine. Sounds like there was something else going on. If I were told by a mechanic that stalling on a roundabout could be remedied by changing the cam belt, I would find a different mechanic.

Ok well timing was not the issue in that case, I’m only guessing ....but what I described was happening and after new cam belt and tensioner adjustment plus water pump all was well ..smoother performance less rattle .. gears suddenly seemed more natural and correct it was like a new van .. I had hired a few by this point and mine was suddenly driving like a new van. Perhaps the tension of the cam belt ?
To be clearer the problem before was I can only explain that it felt like I needed another gear between second and third whenever I slowed at a junction .. maybe that may help to explain ? Anyhow after the work done the problem went away completely and very very noticeably .

 

[DaveD]

Ok well timing was not the issue in that case, I’m only guessing ....but what I described was happening and after new cam belt and tensioner adjustment plus water pump all was well ..smoother performance less rattle .. gears suddenly seemed more natural and correct it was like a new van .. I had hired a few by this point and mine was suddenly driving like a new van. Perhaps the tension of the cam belt ?
To be clearer the problem before was I can only explain that it felt like I needed another gear between second and third whenever I slowed at a junction .. maybe that may help to explain ? Anyhow after the work done the problem went away completely and very very noticeably .

I'm assuming that no other work was done at the same time, no service or anything except cambelt / water pump?

 

[osman]

I'm assuming that no other work was done at the same time, no service or anything except cambelt / water pump?

Nothing else at all it had a full service about a month or so before that’s when the water pump showing signs of leakage was flagged .. the water pump got worse so booked it in and cam belt change was due so had both jobs done at the same time .. nothing else

 

[DXX]

The mechanic would have of noticed straight away if the belt had been previously installed incorrectly as they would not of been able to install the locking pins before stripping down.
Not totally unheard of for mechanics to dishonestly exchange components in the hope that the one they take off to sell or use is in better condition than the one they put on.
Just maybe you got the better deal and they now have the duff component.

 

[Jamie2.0]

Got a price from the local independent VW guys today.... all in, so cam belt, pump and tensioners, break fluid and a/c and courtesy car inc VAT £601, that’s only £6 more VW wanted without vat to do just cambelt and pump!

 

[Niknak]

Just to clear up some confusion around vag group belts and timing both the fuel pump pulley and the cam pulley are adjustable to get the timing spot on, some lazy mechanics won’t correctly adjust this or simply don’t understand what the purpose is, not only are they there to be able to get the timing spot on but also the tension. So yes it is possible for the engine to run better after a new correctly fitted belt as the timing can go out slightly as the belts naturally wear and stretch,

 

[clarinetbcn]

The inspection and proper adjustment of the cam belt tensioner is included in the official VW recommended cam belt inspection every 40,000km. Just had mine done at the last service at 84.000km. Sounds like @osman was dealing with the UK practice of skipping the tensioner and belt inspection (he did mention clattering had gone away) and just needlessly replacing the belt every four years, which goes against VW's service recommendation, but in his case the water pump was faulty so it did make sense to replace the belt at the same time, whether it needed it or not.

 

[osman]

Got a price from the local independent VW guys today.... all in, so cam belt, pump and tensioners, break fluid and a/c and courtesy car inc VAT £601, that’s only £6 more VW wanted without vat to do just cambelt and pump!

Hmmm I had mine done pump cam belt tensioners coolant etc by breeze who I guess are a vw centre and it cost £588 inc vat and I had a courtesy car ..

 

[oldiebut goodie]

I think there may be a basic misunderstanding about ignition timing, which on diesel motors is controlled by the compression cycle and glow plugs and is not adjustable as there are no spark plugs, injection timing of the fuel, which is electronically controlled, and cam belt timing, which controls the physical relationship between the movement of the valve train and the pistons. If that is not correct there could be catastrophic damage to the engine, even if the belt itself is in perfect condition. Sounds like there was something else going on. If I were told by a mechanic that stalling on a roundabout could be remedied by changing the cam belt, I would find a different mechanic.

Ignition timing controlled by glow plugs?
Not on any diesel engine that I have worked on in the last 50 years. You must have some very odd engines there in Spain.

 

[clarinetbcn]

Ignition timing controlled by glow plugs?
Not on any diesel engine that I have worked on in the last 50 years. You must have some very odd engines there in Spain.

No, same as everywhere, We do however read posts before answering: Ignition in a diesel motor takes place when the compression cycle of the piston compresses the fuel/air mixture, heating it to the point that it is ignited by the hot glow plug, which is not adjustable. This is why diesel motors have compression ratios much higher than petrol ones. The ignition is caused by compression heat in contact with the residual heat of the glow plug from the previous explosion, not a spark.

 

[Niknak]

Ignition timing controlled by glow plugs?
Not on any diesel engine that I have worked on in the last 50 years. You must have some very odd engines there in Spain.

Ignition timing controlled by glow plugs?
Not on any diesel engine that I have worked on in the last 50 years. You must have some very odd engines there in Spain.

Did

No, same as everywhere, We do however read posts before answering: Ignition in a diesel motor takes place when the compression cycle of the piston compresses the fuel/air mixture, heating it to the point that it is ignited by the hot glow plug, which is not adjustable.

No sorry but the glow plugs don’t work all the time and do not ignite the fuel air mix, it’s the compression of the fuel air mix that creates the heat for it to ignite

 

[oldiebut goodie]

Don't be silly!
The glow plug is only in operation when the engine is cold to aid starting.
I suggest that you learn the operation of a compression ignition ( diesel) engine before you start making statements like that.

 

[Niknak]

Also you can alter diesel ignition timing with pump timing some of you might be old enough to remember this when having to dti the fuel pumps

 

[Niknak]

I do love a bit of armchair automotive engineering

 

[oldiebut goodie]

I don't know how he thinks a Transit engine worked without any glowplugs!

 

[Niknak]

Lol I know cracks me up, wonder if they could explain how a 2 stroke diesel works

 

[Niknak]

Showing our ages

 

[clarinetbcn]

In-cylinder glow plugs are only heated electrically for cold starting. During at temperature running they serve a secondary function of emitting residual heat from the previous combustion to aid in efficient combustion of the compressed fuel/air mixture when the fuel is injected. A glow plug has to be heated to glowing to start a cold engine. Does anyone think it then cools off once the electrical current is turned off?

 

[oldiebut goodie]

And in a Transit engine?
Don't try to teach grandmother to suck eggs!